This invention relates to a grindstone adapter which enables to remove and attach of a grindstone one-touch for use in electric tools and air tools such as a hand polisher, a disc grinder, and a disc sander etc. equipped with a grindstone having a small diameter (smaller than 125 mm, for example) and operated at low speed (a revolution speed smaller than 4,000 rpm, or a peripheral speed smaller than 1,000 m/min, for example).
A one-touch removable device which enables engaging/disengaging between a drive-side coupling (input boss) connected to a motor (reducer) output shaft for a hand polisher and a grindstone holder (grindstone pad etc.), has so far been proposed in various types (Japanese Unexamined Utility Model Publication No. 58-55845, No. 58-8562 & No. 62-8063). However, these devices are tools for holding their engaging states by utilizing a friction of engaging portions between a drive-side coupling and a grindstone holder or a friction of an elastic ring installed between the two, so that these devices offer a small holding force and are apt to be disengaged. Also, these devices are ready to be worn out due to vibration which will occur when transferring a torque, and still more apt to be disengaged due to looseness. Since a centering function for maintaining the grindstone holder at its center is weak, the device is more easily affected by the vibration from this aspect too and readily suffered from an abnormal wear of the grindstone and run-out of its center. Further, there has been such a trouble that the holder is disengaged when a torque is applied to it in a reverse direction.